Electrical cables

ABSTRACT

A single wire cable conductor consists of an inner part (constituting the major proportion of the cross-sectional area of the conductor) of an aluminium alloy of the kind known as &#39;&#39;&#39;&#39;nonheat-treatable&#39;&#39;&#39;&#39; and having a tensile strength within a range from 155 to 463 MN/m2(10-30 tonf/in2) and an electrical conductivity within the range 26.5% to 44.2% IACS, and, bonded to the inner part, an outer part (constituting the minor proportion of the cross-sectional area of the conductor) of copper or a high conductivity copper alloy and having an electrical conductivity of at least 80% IACS. The single wire conductor may constitute the wire or one of the wires of a single or multiple wire conductor of an electric cable, such as a wiring cable, an aircraft cable or a telecommunication cable.

United States Patent 11 1 ,Raw et al.

1 Mar. 5, 1974 ELECTRICAL CABLES [75] Inventors: Peter Michael Raw, London;

Rodway Albert Robbins, lckenham, both of England [7 3] Assignee: British Insulated Gallenders Cables Limited, London, England 22 Filed: Feb. 14, 1973 21 Appl. No.: 332,382

Related US. Application Data [63] Continuation-in-part of Ser. No. 124,058, March 15,

1971, abandoned.

[30] Foreign Application Priority Data Mar. 16, 1970 Great Britain 12509/70 [52] US. Cl. 174/128, 174/110 R, 174/113 R, 174/126 CP, 174/27 [51] Int. Cl. ..H01b l/02, HOlb 11/02v [58] Field of Search 174/27, 110 R, 128,126 C, 1'7 4/126 CP, 119 C, 113 R; 29/191.6, 194,

[56] References Cited UNITED STATES PATENTS 3,513,251 5/1970 Schoemer 174/110 R 3,513,252 5/1970 Schoerner 174/110 R 3,513,250 5/1970 Schoemer 174/110 R 3,595,985 7/1971. Zelley 29/19l.6 X 3,463,620 8/1969 Winter 29/191.5 X

FOREIGN PATENTS OR APPLICATIONS 1,582,246 9/1969 France 174/126 CP 1,489,845 7/1967 France 174/126C OTHER PUBLICATIONS Standards For Aluminum Mill Products, The Aluminum Assoc, Eighth Ed. 1965, pp. 10, 21, 74. Metals Handbook, 8th Ed. 1961 Vol. 1 American Soc. of Metals pp. 943-945 & 26.

Primary ExaminerBernard A. Gilheany Assistant Examiner-A. T. Grimley Attorney, Agent, or Firm.l0hn M. Webb [57] ABSTRACT A single wire cable conductor consists of an inner part (constituting the major proportion of the crosssectional area of the conductor) of an aluminium alloy of the kind known as non-heat-treatable" and having a tensile strength within a range from 155 to 463 MN/m (1030 tonflin and an electrical conductivity 9 Claims, 6 Drawing Figures ELECTRICAL CABLES This application is a continuation-in-part of application, Ser. No. 124,058, filed Mar. l5, 1971, now abandoned.

This invention relates to electric insulated wires and cables and to single wire conductors therefor. The invention is principally concerned with cables of the kind generally known as wiring cables and used, for example, for the wiring of buildings, vehicles, aircraft, switchboards, equipment and machinery and comprising one or more single or multiple wire conductors covered with insulating and/or sheathing material, but it is also concerned with cables of the kind generally known as telecommunication cables and including, for instance, television distribution and relay cables, television down leads and radio frequency cables.

A large proportion of cables of these kinds are at present provided with copper conductors and it is often the practice to connect the copper conductors to terminals or connectors utilizing clamping screws or to terminate or interconnect them by a method entailing crimping. An object of the invention is to provide a cable in which the major proportion of a conductor or of each of a number of conductors comprises aluminum but nevertheless the conductor or conductors can besatisfactorily jointed or terminated by those methods used for copper conductors mentioned above.

In accordance with the present invention a cable comprises at least one single or multiple wire conductor, the or each wire consisting of an inner part (constituting the major proportion of the cross-sectional area of the wire) of an aluminium alloy of the kind known as non-heat-treatable and having a tensile strength within a range approximating to that of high conductivity copper, that is to say from 155 to 463 MN/m l-30 tonf/in and an electrical conductivity within the range 26.5% to 44.2% lACS and, bonded to the inner part, an outer part (constituting the minor proportion of the cross-sectional area of the wire) of copper or a high conductivity copper alloy and having an electrical conductivityof at least 80% lACS.

Aluminium alloys having the specified tensile strength and electrical conductivity are covered by the NE and NG series in 8.8. 1476( 1955) and 1475( 1955), where the prefix N indicates non-heat-treatable, E indicates bar form and G indicates wire form, especially N63 (1.25% Mn), NGS (3.5% Mg+0.6% Mn), NG6 (5.0% Mg+l.0% Mn) and NES (4.5% Mg+0.75% Mn).

. Examples of cables in accordance with the invention are house wiring cables, lightweight, high-strength aircraft cables and telecommunication cables.

The invention also includes, for use in a cable in accordance with the invention, a single wire cable conductor consisting of an inner part (constituting the major proportion of the cross-sectional area of the conductor) of an aluminium alloy of the kind known as non-heat-treatable and having a tensile strength within a range approximating to that of high conductivity copper, that is to. say from 155 to 463 MN/m 10-30 tonf/in and an electrical conductivity within the range 26.5% to 44.2% lACS, and, bonded to the inner part, an outer part (constituting the minor proportion of the cross-sectional area of the conductor) of copper or a high conductivity copper alloy and having an electrical conductivity of at least 80% lACS.

According to a further aspect of the invention the single wire cable conductor is formed by a process which incorporates the method of manufacturing copper clad aluminium rod described and claimed in U.S. Pat. application Ser. No. 759,138, now U.S. Pat. No. 3,631,586 and which comprises forming a cold composite billet by surrounding a preformed'billet (constituting the major proportion of the cross-sectional area of the composite billet) of an aluminium alloy of the kind known as non-heat-treatableland having a tensile strength within a range approximating to that of high conductivity copper, that is to say from 155 to 463 MN/m 10-30 tonflin and an electrical conductivity within the range 26.5% to 44.2% lACS, with a close fitting sheath (constituting the minor proportion of the cross-sectional area of the composite billet) of copper of a high conductivity copper alloy and having an electrical conductivity of at least 80% lACS, the contiguous surfaces of the aluminium alloy and copper or copper alloy components of the composite billet being clean and substantially free of surface oxides; directly extruding the Cold composite billet so formed to effect a reduction in cross-sectional area of the composite billet to form a copper clad aluminium alloy rod; and drawing down the copper clad aluminium alloy rod to form a copper clad aluminium alloy wire conductor.

By the expression cold composite billet is meant a k composite billet of which the temperature ,prior to and at the time of its insertion into the extrusion press is lower than the' termperature at which non-heattreatable aluminium-based alloys and copper or copper alloys when in contact alloy.

chining or otherwise working the external surface of a billet of a non-heat-treatable aluminium alloy and/or the internal surface of a tube of copper or a copper alloy that the billet is a close fit in the tube, chemically and/or mechanically cleaning the whole of the mating surfaces of the billet and the tube to remove substantially all oxide and other contaminating films therefrom immediately before fitting the one in or on the other, fitting the one in or on the other and sealing the ends of the composite structure to prevent contact of the cleaned contiguous surfaces with the atmosphere. As a further precaution against oxidation the external surface of the billet and the internal surface of the tube may be purged with a non-oxidizing gas, for example nitrogen, during the cleaning and during the assembly of the two components to form the composite structure. Alternatively the cleaning operation may be carried out in an atmosphere of nitrogen or other nonoxidizing gas or under vacuum. When producing copper clad aluminium alloy rod from a composite billet" formed from two such components it is necessary to effect a reduction in cross-sectional area of the composite billet of at least percent in order to achieve a sound metallurgical bond between the copper or copper alloy sheath and the aluminium alloy core.

of copper alloy is electro-plated thereon. In the Alstan 70 process a layer of copper-based tin alloy is first deposited on the circumferential surface of a billet of a non-heat-treatable aluminium alloy and thereafter a relatively thick layer of copper or of a copper alloy is deposited on the aluminium alloy layer. It will be appreciated that the electro-plating method of building the cold composite billet permits of a reduction in the minimum proportion of copper or copper alloy present as compared with the copper tube method of building a cold composite billet.

Since the pre-treatment of the surface of the billet of non-heat-treatable aluminium alloy by the zincate process, by the Alstan 70 process or by any other suitable pre-treatment process results in the formation of a bond between the electro-deposited copper or copper alloy and the billet of aluminium-based alloy it is not necessary in carrying out the alternative process to effect a minimum reduction in cross-sectional area of the composite billet of 70 percent in order to achieve a bond between the copper sheath and the aluminium alloy core of any rod or wire produced from the composite billet. However such plated composite billets may be extruded and drawn to wire in the same manner and to the same minimum extent as composite billets formed from a tube of copper or of copper alloy and a billet of the aluminium alloy, as such extrusion and drawing of plated composite billets merely consolidates the initial bond between the copper or copper alloy and the aluminum alloy.

Extrusion of a cold composite billet to effect a reduction in cross-sectional area and yield an extrudate in which the copper or copper alloy and the non-heattreatable' aluminium alloy components of the billet are soundly metallurgically bonded at the interface can be effected by the process known as hydrostatic extrusion. In this process the billet in the press container is surrounded by a liquid, usually oil, through which are transmitted the forces necessary to deform the billet and force it throughthe extrusion orifice. Where hydrostatic extrusion is used to effect a reduction in cross-sectional area of a composite billet obtained by fitting a billet of a non-heat-treatable.aluminium alloy in a tube of copper or copper alloy and sealing the ends of the composite structure so formed, the seals at the ends of the composite billet prevent ingress of the liquid between the mating surfaces of the composite billet.

The method of the present invention has the important advantage that a single composite wire conductor with a very thin coating of copper or copper alloy can be formed by drawing down a copper clad non-heattreatable aluminium alloy rod in which the percentage by volume of copper or copper alloy is as low as percent or even lower.

Descriptions will now be given, by wayof example, of a preferred method of making a single composite wire conductor and of typical kinds of cables incorporating such conductors in accordance with the invention.

In a preferred method a single wire conductor of diameter 0.l9 mm (0.0076 inch) and consisting of an inner part of an aluminium-based alloy comprising N156 Z2. MstLQZz M lfinqtbsnqs lat nnsr part, an outer part of copper, the copper constituting approximately 25 percent by volume of the wire, is made by extruding by the hydrostatic extrusion process a composite billet containing about25 percent by volume of copper'and made up in the way described from a billet of the aluminum-based alloy of diameter 30.25 rnrn (1.19 inch) and a length of copper tubing ofapproximately 35mm (1.375 inch) overall diameter using an extrusion ratio-of 5.321, by which is meant that the ratio of cross-sectional area of billet to cross-sectional area of extrudate is 5.3: l to form a copper clad aluminum alloy rod of about 15.24 mm (Qtfijsq ame es and aw sfi the rod b at sss liesraw s B QEUQIQE LEE L EQE conductor.

The examples of cables in accordance with the invention are illustrated in the accompanying drawing, in which:

FIGS. 1 and 2 are cross-sectional views, drawn on enlarged scales, of house wiring cable;

FIGS. 3 and 4 are cross-sectional views, drawn on enlarged scales, of aircraft cables;

FIG. 5 is a cross-sectional view, drawn on an enlarged scale, of a television distribution cable, and

FIG. 6 is a cross-sectional view, drawn on an enlarged scale, of a television relay cable.

The house wiring cable shown in FIG. 1 is a single wire conductor of 2.25 mm diameter consisting of an inner part 1 of an aluminium alloy containing 1.25% Mn and, bonded to the inner part, an outerpart 2 of copper, the copper constituting approximately 10 percent by volume of the conductor. The conductor has an insulating covering 3 of polyvinyl chloride.

The house wiring cable shown in FIG. 2 is a multiple wire conductor comprising 7/085 mm stranded wires 10 each consisting of an inner part 11 of an aluminium alloy containing 1.25% Mn and, bonded to the inner part, an outer part 12 of copper,'the copper constituting approximately 10 percent by volume of the wire. The multiple wire conductor has an insulating covering 13 of polyvinyl chloride.

The aircraft cable shown in FIG. 3 is one of a group of aircraft cables comprising single wire conductors, each having a diameter within the range 0.l mm to 0.9 mm. Each conductor consists of an inner part 21 of an aluminium alloy containing 3.5%-Mg and 0.6% Mn or an aluminium alloy containing 5% Mg and 1% Mn and, bonded to the inner part, an outer part 22 of copper, the copper constituting approximately 25 percent by volume of the conductor. The copper outer part 22 is protected by a thin coating 24 of nickel, silver, tin or tin/lead alloy and the coated conductor has an outer insulating covering 23 of polytetrafluoroethylene, polyvinyl chloride, silicone rubber or one or more layers of tape of a polyimide film coated with a fluorinatedethylene propylene copolymer.

The aircraft cable shown in FIG. 4 is a stranded multiple wire conductor comprising 19/0. 193 mm wires 30. Each wire 30 of the conductor consists of an inner part 31 of an aluminium alloy containing 3.5% Mg and 0.6% Mn or an aluminium alloy containing 5% Mg and 1% Mn and, bonded to the inner part, an outer part 32 of copper, the copper constituting approximately 25 percent by volume of the wire. The copper outer part 32 is protected by a thin coating 34 of nickel, sliver, tin or tin/lead alloy. The multiple wire conductor has an insulating covering 33 of polytetrafluoroethylene, polyvinyl chlpride, silicone rubber or one or more layers of tape of a polyimide film coated with a fluorinatedethylene propylene copolymer.

The television distribution cable shown in FIG. 5 comprises a single wireconductor 41 of diameter 1.22 mm covered with an insulating layer 42 of cellular polythene, an inner braided conductor 43 of wires of 0.15 mm diameter, an intersheath 44 of polyvinyl chloride having a radial thickness of 0.64 mm, an outer braided conductor 45 of wires of 0.15 mm diameter, and an outer sheath 46 of polyvinyl chloride. The wire of the cable conductor 41 and each wire of the braided conductors 43 and 45 consists of an inner part of an aluminium alloy containing 5.0% Mg and 1.0% Mn and, bonded to the inner part, an outer part of copper, the copper constituting approximately by volume of the wire. 7

The television relay cable shown in FIG. 6 comprises an assembly of pairs of insulated conductors consisting of six pairs 54 of single wire conductors 55 of diameter 0.46 mm each covered with an insulating layer 56 of polythene, the six pairs being arranged to lie helically around a central core 50 consisting-of three pairs 51 of single wire conductors 52 of diameter 0.42 mm each covered with an insulating layer 53 of polythene. The assembly of pairs is wrapped with a helical lapping 57 of polyethylene terephthalate tape and is enclosed in an outer sheath 58 of polyvinyl chloride. The conductors of each pair 51 and 54 each consist of a wire having an inner part of an aluminium alloy containing 5.0% Mg and 1.0% Mn and, bonded to the inner part, an outer part of copper, the copper constituting l0-l5 percent by volume of the wire.

We claim:

l. A single wire cable conductor consisting of an inner part (constituting the major proportion of the cross-sectional area of the conductor) of an aluminium alloy of the kind known as non-heat-treatable and having a tensile strength within a range from 155 to 463 MN/m 1030 tonflin and an electrical conductivity within the range 26.5% to 44.2% IACS and, bonded to the inner part, an outer part (constituting the minor proportion of the cross-sectional area of the conductor) of a metal selected from the group of metals consisting of copper and a high conductivity copper alloy and having an electrical conductivity of at least 80% lACS.

2. A single wire cable conductor as claimed in claim 1, wherein the outer part constitutes approximately percent by volume of the wire.

3. A single wire cable conductor as claimed in claim 1, wherein the outer part constitutes approximately 10 percent by volume of the wire.

4. A single wire cable conductor as claimed in claim 1, wherein the aluminiumalloy contains sufficient manganese to give it a tensile strength within the specified range.

5. A single wire cable conductor as claimed in claim 1, wherein the aluminium alloy contains sufficient magnesium to give it a tensile strength within the specified range. 6. An electric cable comprising at least one conductor comprising at least one wire consisting of an inner part (constituting the 'major proportion of the crosssectional area of the wire) of an aluminium alloy of the kind known as non-heat-treatable and having a tensile strength within a range from 155 to 463 MN/m 10-30 tonf/in) and an electrical conductivity within the range 26.5% to 44.2% lACS and, bonded to the inner part, an outer part (constituting the minor proportion of the cross-sectional area of the wire) of a metal selected from the group of metals consisting of copper and a high conductivity copper alloy and having an electrical conductivity of at least IACS.

7. An electric wiring cable comprising a conductor comprising at least one wire consisting of an inner part of an aluminium alloy of the kind known as non-heattreatable and having a tensile strength within a range from to 463 MN/m 10-30 tonf/in and an electrical conductivity within the range 26.5% to 44.2% IACS and, bonded to the inner part, an outer part of a metal selected from the group of metals consisting of copper and a high conductivity copper alloy and having an electrical conductivity of at least 80% IACS, the outer part constituting approximately 19 percent by volume of the wire.

8. An aircraft electric cable comprising a conductor, comprising at least one wire consisting of an inner part of an aluminium alloy. of the, kind known as non-heattreatable and having a tensile strength within a range from 155 to 463 MN/m (10-30 tonflin and an electrical conductivity within the range 26.5% to 44.2% lACS and, bonded to the inner part, an outer part of a metal selected from the group of metals consisting of copper and a high conductivity copper alloy and having an electrical conductivity of at least 80% IACS, the outer part constituting approximately 25 percent by volume of the wire.

9. A telecommunications cable comprising at least one conductor comprising at least one wire consisting of an inner part of an aluminium alloy of the kind known as ,non-heat-treatable and having a tensile strength within a range from 155 to 463 MN/m 10-30 tonf/in) and an electrical conductivity within the range 26.5% to 44.2% lACS and, bonded to the inner part, an outer part of a metal selected from the group of metals consisting of copper and a high conductivity copper alloy and having an electrical conductivity of at least 80% lACS, the volume of the outer part lying in the range 10 to 15 percent by volume of the wire.

Y STATES PATENT OFFICE CERTIFICATE 0F CORRECTION Patent No- 3,795,760 Dated March 5, 1974 Inventofls) Peter Michael Raw et a1..

It is certified that er rcrappea rs in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

' On the first page of the patent On the line listing the Assigneez, Ga,ll en c 1er'vsshould read Ca11ender's--.

ehhh 1ce1umh- 6 Line 28 -19 percentshould read ,--l0 percent--.

- Signe c l andrsealee'd' this el 9th day of November 1974.-

I (SEAL) Attest: I I

MecoY M. GIBSON JR. h Q 0. MARSHALL DANN 'Attesting Officer" Ccxmnissioner of Patents FORM PC4050 (10-69) I u.s. GOVERNMENT PRINTING omc: 1909 o-ass-asa,

ITTN ITEDY sTATEs PATENT ()FFICE CERTIFICATE OF CORRECTION- Par n No- 3. 795, 760 Dated March 5, 1.914

Inventofls) Peter Michael Raw et a1.

7 It is certified that error, appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

On the first page of the patent on the line listing the Assignee; Gal1end.er',s

should read --Ca'l1ender's-.

wwl

Clalirh 7.Co1umn 6 Line 28 1 9 percen .sheuld read 10 percent- Signed an rhsale'd this 19th day of November. 1974.

I (SEAL) Attest:

McCOY M. GIBSON JR. c. MARSHALL DANN Attesting Officer Commissioner of Patents 1 FORM po'wso USCOMM-DC 60376-P69 I i ".5. GOVERNMENT PRINTING OFFICE 2 '99 0-365-334, 

2. A single wire cable conductor as claimed in claim 1, wherein the outer part constitutes approximately 25 percent by volume of the wire.
 3. A single wire cable conductor as claimed in claim 1, wherein the outer part constitutes approximately 10 percent by volume of the wire.
 4. A single wire cable conductor as claimed in claim 1, wherein the aluminium alloy contains sufficient manganese to give it a tensile strength within the specified range.
 5. A single wire cable conductor as claimed in claim 1, wherein the aluminium alloy contains sufficient magnesium to give it a tensile strength within the specified range.
 6. An electric cable comprising at least one conductor comprising at least one wire consisting of an inner part (constituting the major proportion of the cross-sectional area of the wire) of an aluminium alloy of the kind known as ''''non-heat-treatable'''' and having a tensile strength within a range from 155 to 463 MN/m2(10-30 tonf/in2) and an electrical conductivity within the range 26.5% to 44.2% IACS and, bonded to the inner part, an outer part (constituting the minor proportion of the cross-sectional area of the wire) of a metal selected from the group of metals consisting of copper and a high conductivity copper alloy and having an electrical conductivity of at least 80% IACS.
 7. An electric wiring cable comprising a conductor comprising at least one wire consisting of an inner part of an aluminium alloy of the kind known as ''''non-heat-treatable'''' and having a tensilE strength within a range from 155 to 463 MN/m2(10-30 tonf/in2) and an electrical conductivity within the range 26.5% to 44.2% IACS and, bonded to the inner part, an outer part of a metal selected from the group of metals consisting of copper and a high conductivity copper alloy and having an electrical conductivity of at least 80% IACS, the outer part constituting approximately 19 percent by volume of the wire.
 8. An aircraft electric cable comprising a conductor, comprising at least one wire consisting of an inner part of an aluminium alloy of the kind known as ''''non-heat-treatable'''' and having a tensile strength within a range from 155 to 463 MN/m2(10-30 tonf/in2) and an electrical conductivity within the range 26.5% to 44.2% IACS and, bonded to the inner part, an outer part of a metal selected from the group of metals consisting of copper and a high conductivity copper alloy and having an electrical conductivity of at least 80% IACS, the outer part constituting approximately 25 percent by volume of the wire.
 9. A telecommunications cable comprising at least one conductor comprising at least one wire consisting of an inner part of an aluminium alloy of the kind known as ''''non-heat-treatable'''' and having a tensile strength within a range from 155 to 463 MN/m2 (10-30 tonf/in2) and an electrical conductivity within the range 26.5% to 44.2% IACS and, bonded to the inner part, an outer part of a metal selected from the group of metals consisting of copper and a high conductivity copper alloy and having an electrical conductivity of at least 80% IACS, the volume of the outer part lying in the range 10 to 15 percent by volume of the wire. 